Since this valve (and most of the EFI pumps Ive seen) use hose barbs
rather than AN fittings what type of hose and clamps are you using?>>

norm2 wrote:

The return valve is on the low pressure side.  I suppose that if a person
wanted to be conservative about it you could mount the valve inside the fuel
tank, or in a fuel tight vented compartment.  This is a Pollack valve, and
they make a marine version out of stainless that I would guess has pipe
fittings.  As far as clamps, the 'open them with a pliers' that is used on
automotive is probably the best.  They continue to squeeze even if the hose
relaxes.  Worm gear clamps are bad business.

<<IMHO You should be using AN lines.

See Kinsler for stuff with  AN fittings. This is probably the most
important system in your airplane. It does not pay to nickel and dime it.>>

Flare fittings are about the poorest connection you can put in a pressurized
fluid joint (the only ones worse would have to be pipe thread...).  Of
course, the aircraft industry is going to take another 50 years to approve
anything different.  You have to watch the number of joints (especially high
pressure joints) and use the best setup that you can.  I am going to have a
header made that couples the injection pumps and outputs to an AN fitting
(probably through a pipe fitting adapter), use an appropriate aircraft
quality pressure line to the fuel rail, and similar from the pressure
regulator.  I have to think about that return valve connection.  The barbed
fittings have millions of miles on them in the automotive buisness, even at
injection pressure.  But there is probably a better way to handle it in the
engine compartment on a plane.  I think that some of the discussions about
moving the injectors to the cool side of the engine really makes a lot of
sense.  Along with that, if you could line up the injectors so as to use one
fuel rail that would eliminate another set of leakage points.  Somehow,
there is probably a system where the high pressure pump is mounted right to
the fuel rail such that you have no flexible lines with high pressure on
them.  Something to think about...

 
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